CA2683215C - Method to provide variability in fluid flow rates in a well - Google Patents

Abstract

A method for providing variability and fluid flow rates in a well includes using a plurality of main valves arranged to form an operating cluster, each main valve being controlled by a pilot valve.

Description

METHOD TO PROVIDE VARIABILITY IN FLUID FLOW RATES IN A WELL
Related Application This application is a divisional application of Canadian Patent Application No. 2,517,408 filed August 29, 2005 and claims priority from therein.
Background of the Invention [0001] Field of Invention. The present invention pertains to pilot valves used in downhole completions, and particularly to a pilot valve using an actuator to control the state of the pilot valve, and thereby the state of the main valve.

[0002] Related Art. Pilot valves are used in gas lift product lines such as intermittent gas lift applications. Existing pilot valves are typically driven by a bellows operating in response to a pressure differential, similar to what is used in other types of gas lift valves.
Although the present invention can be used for intermittent gas lift, it is not limited to that application.

[0003] Actuator valves such as solenoid valves, for example, are used in various industrial and downhole applications. Because of the linear relationship between the port size and solenoid force requirement, pilot valves have been used in many solenoid-actuated valves to maximize pressure ratings. In many existing downhole tool designs, two bellows are used to seal and isolate reservoir fluids from the fluid in the interior of the solenoid. In addition, the two-bellows configuration allows the pressure to balance between those fluids. The most intuitive way of configuring two bellows is to have two separate bellows; one for sealing and the other for pressure balancing. However, because of space constraints, it may be more advantageous to achieve both functions using only one fluid contact surface.
In US Patent 2,880,620, Bredtschneider describes a system having two telescoping bellows for this purpose. In US Patent 5,662,335, Larsen describes a system that achieves the same purpose by assembling two bellows in an end-to-end arrangement.
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Summary [0004] The present invention provides for a pilot valve used in a well and in which the state of the pilot valve is controlled by an actuator.

[0004a] According to an aspect of the invention, there is provided a method to provide variability in fluid flow rates in a well comprising: arranging a plurality of main valves in an operating cluster in which the main valves of the plurality of main valves are in close proximity to each other at approximately the same depth downhole in a wellbore; controlling each main valve by a pilot valve, the pilot valve being selectively actuated by a surface controlled actuator independently of pressure acting on the pilot valve downhole; and adjusting flow area at the same depth downhole by opening a desired number of the main valves via selective actuation of the pilot valves.

[0005] Advantages and other features of the invention will become apparent from the following description and drawings.
la Brief Description of Drawings [0007] Figure 1 shows a schematic view of a piloting actuator valve constructed in accordance with the present invention.
[0008] Figure 2 is a schematic view of the piloting actuator valve of Figure 1 showing a spring disposed in the main valve.
[0009] Figure 3 is a schematic view of an embodiment of a solenoid used in the piloting actuator valve of Figure 1.
[0010] Figure 4 is a schematic view showing a cluster of piloting actuator valves being used in a well.
Detailed Description [0011] Figure 1 shows a piloting actuator valve 10 having a housing 12 enclosing a pilot valve 14 and a main valve 16. Pilot valve 14 comprises an actuator 18, bellows 20, 22, and a plunger 24. Actuator 18 can be one of various mechanical or electromechanical devices. For example, actuator 18 may be a solenoid, a piezoelectric device, a shape-memory alloy, a linear motor, or a conventional electric motor. In the embodiment of Figure 1, and in the discussion below, a solenoid is described as the actuating member.
However, the above alternatives may readily be adapted to replace the solenoid and serve as the actuating member.
[0012] Referring to Figure 1, solenoid 18 comprises a core 26 and windings 28 wrapped on core 26. Windings 28 at least partially circumferentially enclose one end of plunger 24. The opposite end of plunger 24 has a sealing surface 30 that mates with a pilot seat 32. Bellows 20, 22 mount to housing 12 inside a cavity 34 in housing 12 and to plunger 24, at least partially circumferentially enclosing plunger 24. Plunger 24 extends into cavity 34. A pilot injection port 36 allows fluid communication between cavity 34 and the exterior of housing 12. The exterior of housing 12 is subjected to fluids upstream of piloting actuator valve 10.

[0013] In the embodiment of the Figure 1, bellows 20, 22 are disposed in housing 12 in a telescoping arrangement. Bellows 20, 22 provide a seal between the downhole fluids and actuator 18. Bellows 20, 22 also provide pressure balancing between the fluids in the interior of actuator 18 and the downhole fluids in contact with bellows 20, 22. In addition, the spring force of bellows 20, 22 may be used as a return mechanism of plunger 24. An optional spring or springs (not shown) may also be used to provide this force.
[0014] Main valve 16 comprises a piston 38 disposed in a main chamber 40 within housing 12. Piston 38 has a piston head 42 on one end that divides main chamber 40 into first and second sides. Piston head 42 is in sliding, sealing contact with the walls of main chamber 40. On the end of piston 38 opposite piston head 42 is a main seal 44.
Main seal 44 seals against a main seat 46 when main valve 16 is closed. Piston 38 has a piston passageway 48 that allows fluid communication between the first side of main chamber 40 and the downstream side of main valve 16 (typically production tubing). A pilot passageway 50 allows fluid communication between cavity 34 and the first side of main chamber 40 when sealing surface 30 is not engaged with pilot seat 32. A main injection port 52 allows fluid communication between the second side of main chamber 40 and the exterior of housing 12 (typically the well annulus). An optional spring 54 (Figure 2) may be used to improve functional characteristics of main valve 16.
[0015] In the embodiment shown in Figure 3, solenoid 18 has a plunger ring 56 and a retainer ring 58. Plunger ring 56 slides on plunger 24 but its movement is limited by retainer ring 58. Electrical current passing through windings 28 produces magnetic forces on plunger 24 and plunger ring 56 that, in this embodiment, tend to pull plunger 24 into an upper gap 60 while pulling plunger ring 56 into a lower gap 62. The force on plunger ring 56 is initially transferred to plunger 24 via shoulder 64. Because upper gap 60 is larger than lower gap 62, as plunger 24 travels into and narrows upper gap 60, lower gap 62 narrows and then closes.
As plunger 24 continues moving to further narrow upper gap 60, plunger ring 56 slides on plunger 24 until upper gap 60 closes completely. Because the magnetic force is inversely proportional to the width of the gap, the force created at lower gap 62 contributes significantly because of the smaller gap distance. Furthermore, this increase in force at the original position of plunger 24 is not achieved by sacrificing travel because the larger upper gap is the total intended travel of plunger 24.

[0016] There are various operational states for piloting actuator valve 10, including permutations of pilot valve 14 being open or closed and injection fluid pressure being greater or less than production fluid pressure.
[0017] In operations in which solenoid 18 is energized, core 26 is magnetically energized by windings 28. In the arrangement shown, the magnetic field exerts a pulling force on plunger 24. Solenoid 18 opens pilot valve 14 by pulling sealing surface 30 from sealing engagement with pilot seat 32. Alternative actuator mechanism would similarly control the state of pilot valve 14.
[0018] If injection fluid pressure exceeds production fluid pressure while pilot valve 14 is open, the net force on piston 38 drives piston 38 such that main valve 16 is held in its open state, and injection fluid flows downhole. That occurs because fluid pressure entering through pilot injection port 36 passes through pilot passageway 50 and bears on piston head 42. Fluid flow is choked in piston passageway 48. Therefore, the pressure of the fluid drops from injection pressure at one end of piston passageway 48 to production pressure at the other end. Since the injection fluid pressure is greater than the production fluid pressure bearing on the opposite end of piston 38, main seal 44 is driven off of main seat 46. Injection fluid entering through main injection port 52 flows through open main valve 16.
[0019] If production fluid pressure exceeds injection fluid pressure while pilot valve 14 is open, piston 38 is similarly driven such that main valve 16 is held in its open state. That is because the higher pressure production fluid passes through piston passageway 48 in to the first side of main chamber 40, through pilot passageway 50 into pilot chamber 34, and out pilot injection port 36. However, the flow restrictions represented by those various passageways and ports allow pressure in first side of main chamber 40 to build up to nearly that of the production fluid pressure, and that pressure bears on one end of piston head 42.
Pressure in the second side of main chamber 40 is the lower injection fluid pressure, and that bears on the other end of piston head 42. Thus, the forces on piston 38 are not balanced and main valve 16 is held open.
[0020] When pilot valve 14 is closed, production fluid pressure is communicated through piston passageway 48 to the first side of main chamber 40. If the injection fluid pressure passing through main injection port 52 exceeds the production fluid pressure, the net force on piston 38 drives piston 38 such that main valve 16 is held in its closed state, and there is no flow through piloting actuator valve 10. If the injection fluid pressure is less than the production fluid pressure, the net force on piston 38 drives piston 38 such that main valve 16 is held in its open state, and production fluid flows through main injection port 52. An optional backflow check valve (not shown) can be used to avoid flow from the production to the injection side.
[0021] When pilot valve 14 is closed, and if injection pressure exceeds production fluid pressure, injection pressure exerted by injection fluid passing through pilot injection port 36 effectively acts on all surfaces of plunger 24 except the portion extending into pilot passageway 50, which is subjected to production fluid pressure. Because bellows 20, 22 balance the pressure on either side of bellows 20, 22, pressure applied to the end of plunger 24 within solenoid 18 equals the injection pressure. Thus, the injection pressure acts to keep pilot valve 14 closed. One or more springs may be used to bias plunger 24 to the closed position as well, as can the stiffness of bellows 20, 22. Thus, the force required to open or close pilot valve 14 can be adjusted to accommodate various operating environments.
[0022] Although not critical to the valve function, another design feature in this invention is the main seal 44 and main seat 46. The seal created between the lower side of the main seat 46 and the main seal 44 can be designed to optimize the flow geometry to minimize losses. For example, a venturi profile can be used.
[0023] The present invention can operate as an open/close mechanism. It is often desirable in a gas lift system to have variability in flow area. Providing a plurality of piloting actuator valves 10 as shown in Figure 4 allows an operator to achieve this variability. The piloting actuator valves 10 may be placed at the same depth or in close proximity to one another in a subterranean well 66 to form an operating cluster 68. Each piloting actuator valve 10 can be opened or closed independently to provide the desirable flow area. Piloting actuator valves 10 in a operating cluster may have similar flow areas or different flow areas to optimize flow rates and adjustability.
[0024] Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications =

= 78543-192F
[0025]
are intended to be included within the scope of this invention,as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a mail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures.

Claims (2)

1. A method to provide variability in fluid flow rates in a well comprising:
arranging a plurality of main valves in an operating cluster in which the main valves of the plurality of main valves are in close proximity to each other at approximately the same depth downhole in a wellbore;
controlling each main valve by a pilot valve, the pilot valve being selectively actuated by a surface controlled actuator independently of pressure acting on the pilot valve downhole; and adjusting flow area at the same depth downhole by opening a desired number of the main valves via selective actuation of the pilot valves.

2. The method of claim 1 in which using a plurality of main valves further comprises using the main valves for downhole flow control, gas lift, chemical injection, or water injection.